Laboratory of Food Microbiology and Hygiene, Department of Food Science and Technology, Faculty of Agriculture, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
Appl Environ Microbiol. 2010 Apr;76(7):2181-91. doi: 10.1128/AEM.02430-09. Epub 2010 Feb 5.
A survey on the time-temperature conditions of pasteurized milk in Greece during transportation to retail, retail storage, and domestic storage and handling was performed. The data derived from the survey were described with appropriate probability distributions and introduced into a growth model of Listeria monocytogenes in pasteurized milk which was appropriately modified for taking into account strain variability. Based on the above components, a probabilistic model was applied to evaluate the growth of L. monocytogenes during the chill chain of pasteurized milk using a Monte Carlo simulation. The model predicted that, in 44.8% of the milk cartons released in the market, the pathogen will grow until the time of consumption. For these products the estimated mean total growth of L. monocytogenes during transportation, retail storage, and domestic storage was 0.93 log CFU, with 95th and 99th percentiles of 2.68 and 4.01 log CFU, respectively. Although based on EU regulation 2073/2005 pasteurized milk produced in Greece belongs to the category of products that do not allow the growth of L. monocytogenes due to a shelf life (defined by law) of 5 days, the above results show that this shelf life limit cannot prevent L. monocytogenes from growing under the current chill chain conditions. The predicted percentage of milk cartons-initially contaminated with 1 cell/1-liter carton-in which the pathogen exceeds the safety criterion of 100 cells/ml at the time of consumption was 0.14%. The probabilistic model was used for an importance analysis of the chill chain factors, using rank order correlation, while selected intervention and shelf life increase scenarios were evaluated. The results showed that simple interventions, such as excluding the door shelf from the domestic storage of pasteurized milk, can effectively reduce the growth of the pathogen. The door shelf was found to be the warmest position in domestic refrigerators, and it was most frequently used by the consumers for domestic storage of pasteurized milk. Furthermore, the model predicted that a combination of this intervention with a decrease of the mean temperature of domestic refrigerators by 2 degrees C may allow an extension of pasteurized milk shelf life from 5 to 7 days without affecting the current consumer exposure to L. monocytogenes.
对希腊巴氏杀菌奶在运输到零售、零售储存和家庭储存及处理过程中的时间-温度条件进行了调查。调查数据用适当的概率分布进行了描述，并引入到巴氏杀菌奶中李斯特菌生长模型中，该模型经过适当修改以考虑到菌株变异性。基于上述组成部分，应用概率模型通过蒙特卡罗模拟来评估巴氏杀菌奶冷链过程中李斯特菌的生长情况。模型预测，在市场上销售的巴氏杀菌奶纸盒中，有 44.8%的纸盒中的病原体将在食用前生长。对于这些产品，估计李斯特菌在运输、零售储存和家庭储存过程中的总生长量为 0.93 对数 CFU，95%和 99%的百分位数分别为 2.68 和 4.01 对数 CFU。尽管根据欧盟法规 2073/2005，希腊生产的巴氏杀菌奶属于由于 5 天的保质期（法律规定）不允许李斯特菌生长的产品类别，但上述结果表明，在当前的冷链条件下，这个保质期限制并不能阻止李斯特菌生长。预测初始污染 1 个细胞/1 升纸盒的巴氏杀菌奶纸盒的百分比-在食用时病原体超过 100 个细胞/ml 的安全标准，为 0.14%。使用秩相关，概率模型用于对冷链因素进行重要性分析，同时评估了选定的干预和保质期延长方案。结果表明，简单的干预措施，如在家庭储存巴氏杀菌奶时将冰箱门搁架排除在外，可以有效地减少病原体的生长。冰箱门搁架是家庭冰箱中最温暖的位置，消费者最常将其用于家庭储存巴氏杀菌奶。此外，模型预测，这种干预措施与将家用冰箱的平均温度降低 2 摄氏度相结合，可能会使巴氏杀菌奶的保质期从 5 天延长至 7 天，而不会影响当前消费者接触李斯特菌的情况。
